The present invention relates generally to vehicle speed sensors and, in particular, to a tone wheel apparatus and a method of assembling the tone wheel on a vehicle wheel bearing seal.
The U.S. Pat. No. 3,482,129 discloses an inductor generator with a self-lubricating bearing. A tone wheel is mounted on a Teflon bearing ring and has fingers which engage fingers formed on a drive ring on the generator axle shaft.
The U.S. Pat. No. 3,626,226 discloses a cup shaped tone wheel pressed onto a pilot on a wheel hub and having a flange for increasing the surface contact area.
The U.S. Pat. No. 3,772,547 discloses a tone wheel mounted on an end of a tubular sleeve encircling a vehicle axle shaft. The end of the sleeve is swaged over and has a bearing located against the tone wheel by a swaged collar.
The U.S. Pat. No. 4,795,278 discloses a tone wheel in the form of a pulsar gear pressed onto an outer ring of a bearing.
Other types of prior art speed sensors are shown in the FIGS. 1 and 2. In the FIG. 1, as discussed below, there is shown a tone wheel and a wheel bearing support formed as an integral part. One undesirable feature of this apparatus is that the position, size and/or number of sensor apertures cannot be changed easily.
In the FIG. 2, a tone wheel is mounted on a wheel bearing seal by pressing onto an axially extending surface of the wheel bearing seal against a radially extending flange joined to the axially extending surface by a radiused portion. Due to the thicknesses of the parts and the size of the radius, very little contact is made between the parts which can lead to undersirable errors in the speed sensed. For example, misalignment of the tone wheel with respect to a desired plane of rotation can occur which could cause the sensor to miss counts in a sector of the tone wheel spaced too far away from the sensor. Also, relative rotation between the seal and the tone wheel could occur resulting in high or low readings with respect to the actual speed. Furthermore, the tone wheel can scrape and damage the protective coating on the seal during assembly.